Cyclic scheduling in robotic cells producing multiple part types

In this study, the considered problem is design of robotic cell producing multiple parts and consists of machines served by a single gripper robot. A single gripper robot can hold only one part at a time. In the system, while the parts are processing in the machines, transfers between machines and loading/unloading of machines is performed by a single robot. Each parts have to be proceed in all machines, there are specific process time according to parts and machines. In this system, cyclic production is preferred because both the robot performs activities by following computer codes and it is easy to implement and control. "n-unit cycle" as a sequence of robot activities in which the system returns to the same state after producing n parts is handled. In this problem, the aim is generated a solution method to simultaneously determine the optimal part sequence and robot move sequence that maximize throughput or equivalently minimize the long-run average cycle time. In the literature, there is no study that is determining n-unit cycle that minimizes the cycle time for multiple part-type production in m machines to simultaneously determine robot move sequences and part sequence. The mathematical model is developed as an exact solution method. Therefore, for this problem includes scheduling of robot moves and sequencing of parts simultaneously which is shown to be NP-hard, heuristic methods are developed because no available integer solutions are obtained particularly for largescaled problems. Experimental studies is performed to evaluate the performance of the proposed algorithms.